Hey, there's an idea: seize water rights through eminent domain in the drought-afflicted parts of California and auction them off to the highest bidder!
That's not entirely true. Or at least it's more complex than that. Look at what the federal government did in the 1930s. They bought gold at X dollars I believe it was 30 bucks an ounce. They then turned around and raise the price of gold to 33 bucks an ounce. From one perspective the government paid fair market rate, from another perspective they get to dictate fair market rate to at least a certain degree. Theit fiat allows them to have more power over pricing and valuation.
When we look at water rights they can do the same thing. Apparently water is undervalued. This means that the rights to said water are undervalued as well. If the government where to seize the property under eminent domain, they would be seeing it at the undervalued price. At auction they would make the premium of whatever increase they deem necessary to properly value water. They have now made money from a land snatch and grab.